Environmentally friendly water-based treatment agent for improving the phosphate treatment properties of high-strength steel.

Abstract

The present invention belongs to the technical field of surface treatment of metal materials, and particularly relates to an environmentally friendly aqueous treatment agent for improving the phosphatability of high-strength steel. The aqueous treatment agent is prepared by dissolving or dispersing a composition in an aqueous medium. The specific composition of the aqueous treatment agent is: A. A compound selected from compounds containing fluoride ions; B. A compound selected from metal ion compounds containing Cu, Zn, Mn, Ni, and Fe; C. A compound selected from organic acids; D. A compound selected from surfactants. The aqueous treatment agent may be diluted by adding 0 to 20 parts of water to 1 part of the treatment agent before use. The treatment agent can impart excellent phosphatability to the surface of high-strength steel sheets and is mainly applied to the surface modification treatment of high-strength steel.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of metal materials, and in particular, to an environmentally friendly aqueous treatment agent for high-strength coil steel surfaces that can impart excellent phosphatability to the surface of high-strength steel sheets and is mainly applied to surface modification treatment of high-strength steel.

Background Art

[0002] The phosphate treatment process born in the early 20th century is currently widely used in the pre-painting treatment process of automobiles / household appliances. After a century of technological development, a very mature technical system has already been formed in terms of the formulation of phosphate treatment solutions, film-forming mechanisms, and action mechanisms. Phosphate treatment mainly involves contacting a phosphate treatment solution with the surface of a steel sheet, and through acid erosion and the oxidation action of an accelerator, rapidly reducing the hydrogen ion content in the interfacial region, gradually dissociating phosphate ions, and forming metal ions and phosphate precipitates. A phosphate layer that uniformly, finely, and completely covers the metal surface can effectively improve the adhesion of the coating and the corrosion performance under the coating film. Conventional automobile bodies are usually applied with normal cold rolling, and when combined with zinc plating materials and phosphate treatment, good and stable effects can be obtained. Currently, the problem of phosphate treatment application for automotive materials with novel surface characteristics is relatively prominent and is also a research hot spot in the industry.

[0003] In recent years, with the advancement of steel material technology, the applications of ultra-high-strength steel have become increasingly widespread. Particularly in high-strength steel for automobiles, ultra-high-strength steel material technology has entered a stage of rapid development and generalization due to its remarkable effects in terms of safety, environmental protection, and weight reduction. On the other hand, ultra-high-strength steel requires the addition and use of more alloying elements, which directly changes the surface properties of the material. Research has shown that compositions formed by the selective oxidation of elements such as Mn, Si, and Cr tend to be unevenly distributed on the surface of steel sheets, often causing problems such as crystal coarsening and poor coating during the phosphate treatment process, significantly reducing its phosphate-treatability and making it unable to meet the demands of painted applications. In response to this, major steel manufacturers both domestically and internationally have conducted numerous technical studies to optimize the phosphate-treatability of high-strength steel surfaces. Many of these technologies focus on controlling the selective oxidation of elements such as Mn, Si, and Cr on the extreme surface of steel sheets (e.g., CN102834531, CN102482728, CN102534359, CN108368590). This type of patented technology requires effectively balancing the degree of internal oxidation with the oxidation state of the extreme surface while ensuring the control of selective oxidation precipitates on the surface. This results in a narrow process window, high difficulty, and incompatibility with materials of different compositions, requiring process design tailored to the specific material.

[0004] Patents related to phosphate modification treatment technology for high-strength steel surfaces mainly include two technologies: surface electrolytic pickling to remove the oxidized layer and surface flash plating to cover the oxidized layer. Publication numbers CN104136644, CN103124799, CN104508155, and CN103305749 propose a method for removing the oxidized layer on the surface of high-strength steel that affects phosphate treatment properties by a surface electrolytic pickling process for cold-rolled sheets. While this type of technology offers good workability and compatibility with materials of different compositions, it also suffers from high energy consumption, is environmentally unfriendly, and requires the addition of a pickling step, making it unsuitable for conventional high-strength steel production lines.

[0005] Publication number CN104471115 proposed galvanizing the surface of steel sheets with a coverage of 60% or more by flash plating to optimize surface phosphate treatment and mold adhesion. Simultaneously, the publication also reported techniques for producing high-strength steel with good phosphate treatment properties using flash nickel plating or flash iron plating. While this type of technique can impart new stability properties to the surface of high-strength steel materials through the plating layer, it consumes too much energy, is unenvironmentally unfriendly, and requires an additional plating process, making it unsuitable for conventional high-strength steel production lines.

[0006] The development of an environmentally friendly, water-based treatment agent that can optimally control the phosphate treatment properties of high-strength steel surfaces is of great significance for the efficient practical application and widespread use of high-strength steel technology for automobiles. [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective of the present invention is to provide an environmentally friendly water-based treatment agent for optimally modifying the phosphate treatment properties of high-strength steel surfaces. [Means for solving the problem]

[0008] This invention, after theoretical analysis, extensive laboratory scientific research, and practical verification, has finally determined the technical route for an environmentally friendly aqueous treatment agent for good nano-modification of phosphate-treated surfaces. The aqueous treatment agent is formulated to match the surface properties of typical high-strength steel, containing one or more components from among fluorine-containing compounds, metal ion compounds, organic acid compounds, and surfactants. This treatment agent can meet the requirements for application in high-speed continuous production processes of high-strength coil steel and in the manufacturing processes of processed parts. Specifically, the treatment method involves forming a wet film on the steel sheet surface by impregnation, spraying, or roll coating, and rapidly forming a surface-modified layer several nanometers thick from the treatment agent on the steel sheet surface by spraying or baking. This modified treatment layer can form epitaxial active nucleation sites on the steel sheet surface that have the same crystal orientation as phosphate crystals, thereby significantly improving the phosphate-treated properties of high-strength steel sheet surfaces containing high-alloying elements (e.g., Mn, Si, Cr, Mo, etc.) without affecting processing performance such as forming and joining.

[0009] The technical solution of this invention is: An environmentally friendly aqueous surface modification treatment agent for phosphate treatment of high-strength steel products, wherein the surface treatment agent (aqueous treatment agent) is prepared by dissolving or dispersing the composition in an aqueous medium, and the specific composition of the surface treatment agent is: A. Compounds selected from compounds containing fluoride ions; A compound selected from metal ion compounds containing B.Cu, Zn, Mn, Ni, and Fe; C. Compounds selected from organic acids; and D. Compounds selected from surfactants; That is the case.

[0010] The surface treatment agent according to the present invention may be used after diluting it with 0 to 20 parts water in addition to 1 part of the treatment agent. Alternatively, it may be used directly without adding water.

[0011] The metal ions in this invention are not limited to those in a specific valence state. The fluoride ion-containing compound in the aqueous treatment agent according to the present invention includes one or more of the following: ammonium fluorotianoate, ammonium fluorozirconate, potassium fluorotianoate, potassium fluorozirconate, etc. The content of element F in the solution is 0.3 to 1.8 mol / L in molar concentration, preferably 0.3 to 1.7 mol / L, and more preferably 0.6 to 1.1 mol / L. On the one hand, this additive can exert the effect of homogenizing surface etching, and on the other hand, it can deposit titanium or zirconium in a spot-like manner on the material surface, forming nucleation active sites that contribute to phosphate treatment. If the content of element F is less than 0.3 mol / L, the film-forming ability of the surface treatment agent is poor and affects the modification treatment effect, but if the content of element F exceeds 1.8 mol / L, the stability of the surface treatment agent tends to decrease significantly.

[0012] The one or more metal ion compounds containing Cu, Zn, Mn, Ni, and Fe in the aqueous treatment agent according to the present invention include sulfates, carbonates, and nitrates containing copper ions; sulfates, phosphates, formates, and acetates containing Zn ions; phosphates, carbonates, and nitrates containing Mn ions; nitrates and oxalates containing Fe ions; and sulfates, nitrates, and carbonates containing Ni ions. The content of the metal ion compound in the solution is 0.05 to 0.6 mol / L in molar concentration, preferably 0.07 to 0.6 mol / L, and more preferably 0.1 to 0.25 mol / L. The main function of the additive is to further add isomorphic nucleation sites for phosphate crystals. If the content is less than 0.05 mol / L, the effect of effectively adding nucleation sites for phosphate treatment cannot be achieved, but if the content is greater than 0.6 mol / L, the thickness of the modified film layer becomes too large, a uniform passivation effect is formed, and the paintability of the treated surface is directly affected.

[0013] The organic acid compound in the aqueous treatment agent according to the present invention includes organic acid compounds that have complex-forming or chelate-forming functions, such as citric acid, oxalic acid, tannic acid, lactic acid, tartaric acid, and salicylic acid. In some embodiments, the organic acid compound is citric acid, oxalic acid, tartaric acid, or tannic acid. The content of the organic acid compound in the solution is 0.03 to 0.4 mol / L in molar concentration, preferably 0.05 to 0.2 mol / L. The compound has a certain degree of cleaning action on the surface of the steel plate, and some of the reactants formed can adhere to the surface of the steel plate, thereby promoting the rapid nucleation and growth of the phosphate film. If the content is below 0.03 mol / L, the surface cleaning action is clearly reduced, but if the content is above 0.4 mol / L, it significantly affects the stability of the treatment agent system.

[0014] The compounds selected from the surfactants in the surface treatment agent according to the present invention mainly include sodium dodecyl sulfate, sodium dodecyl sulfonate, calcium dodecyl sulfonate, octadecylamine, and triethanolamine. The content of the surface treatment agent compound in the solution is 0.002 to 0.015 mol / L in molar concentration, preferably 0.003 to 0.01 mol / L. The main function of the additive is to improve the film-forming properties of the treatment agent while simultaneously reducing the surface tension after film formation, optimizing the rapid wetting effect between the steel plate surface and the phosphate treatment agent in the pre-painting treatment process, and thereby improving phosphate treatment performance. If the content is below 0.002 mol / L, the optimization of the film-forming properties of the treatment agent becomes less significant, but if the content exceeds 0.015 mol / L, the film-forming quality of the treatment agent is significantly affected, and the effect of optimizing phosphate treatment performance after film formation decreases.

[0015] The environmentally friendly water-based treatment agent for improving the phosphate treatment properties of high-strength steel according to the present invention can be applied to continuous manufacturing lines for pickled high-strength steel and cold-rolled high-strength steel. By forming a wet film on the surface of the steel sheet through impregnation, spraying, roll coating, etc., a nanoscale surface modification layer can be rapidly formed from the treatment agent on the surface of the steel sheet by spraying, baking, etc. The effect of significantly optimizing the phosphate treatment properties of the high-strength steel surface has been achieved.

[0016] In some embodiments, the present invention provides a method for improving the phosphate treatment properties of high-strength steel, comprising treating the high-strength steel with an environmentally friendly water-based treatment agent described herein by impregnation, spraying, roll coating, etc. In some embodiments, the method further includes treating the high-strength steel with a degreasing agent to remove dirt and oil adhering to its surface, then washing it with pure water to remove any remaining alkaline components from the surface, drying it by spraying, and then surface treating the high-strength steel with the environmentally friendly water-based treatment agent. In some embodiments, the high-strength steel is pickled high-strength steel or high-strength steel obtained by cold rolling.

[0017] In some embodiments, the present invention provides a method for phosphate treatment of high-strength steel, which includes treating the surface of high-strength steel using the method described herein, and then sequentially performing degreasing, washing, surface conditioning, phosphate treatment, washing, and drying on the surface-treated high-strength steel to phosphate treatment the high-strength steel.

[0018] In some embodiments, the paper further provides a high-strength steel having a nanoscale surface modification layer formed on its surface by drying the surface treatment agent described herein. After phosphate treatment, the high-strength steel has a phosphate crystal coverage of ≥80%, preferably 100%, a phosphate crystal size of ≤6 μm, preferably ≤4 μm, and a phosphate film weight of ≥2 g / m². 2 Preferably, ≥2.3 g / m 2That is. Thus, in some embodiments, the text further provides a phosphatized steel sheet obtained by phosphatizing the high-strength steel described in the text, wherein the phosphatized crystal coverage is ≧80%, preferably 100%, the phosphatized crystal size is ≦6 μm, and the weight of the phosphate film is ≧2 g / m 2 There is provided a phosphatized steel sheet characterized in that it is. In the present text, the phosphatization described in the text can be carried out using a normal treatment agent (for example, PB-L3065 type phosphatization treatment solution).

Advantages of the Invention

[0019] Beneficial technical effects of the present invention: The present invention provides an environmentally friendly aqueous treatment agent for improving the phosphatization property of high-strength steel so that the surface of the high-strength steel sheet has excellent phosphatization property. The aqueous treatment agent according to the present invention, while being an environmentally friendly aqueous treatment agent, can meet the requirements for application in the high-speed continuous production process of high-strength coil steel and the manufacturing process of processed parts without affecting processing performances such as forming and joining.

Modes for Carrying Out the Invention

[0020] To better understand the present invention, the present invention will be specifically described by way of examples and comparative examples, but the scope of the present invention is not limited by these examples. Hereinafter, the surface treatment agent composition used and the types of steel sheets treated will be described: (1) Test sample plate: The material used in the examples is a typical 80 kg class ultra-high strength steel with a thickness of 1.2 mm, and the component composition is shown in Table 1.

[0021]

Table 1

[0022] (2) Processing and cleaning methods for the sample plates: The above material was processed into 30*70mm sample pieces by shearing, spray-cleaned with an alkaline degreasing agent (pH=11~12) to remove dirt and oil adhering to the surface, then washed with pure water to remove any remaining alkaline components, and dried by blowing with cool air before being prepared for use.

[0023] (3) Composition of water-based surface treatment agent The composition, formulation, and treatment method of the environmentally friendly water-based treatment agent used in the examples are shown in Table 2. However, Comparative Example 4 is a raw surface material that was not surface-treated with the treatment agent.

[0024] [Table 2]

[0025] The surface-treated sample plates obtained in the above examples and comparative examples were treated with 1000 mg / m². 2 After applying rust-preventive oil, the phosphate treatment properties of the pre-painting treatment were evaluated after a one-week period. The pre-painting treatment process in an automobile factory, primarily involving degreasing, surface preparation, and phosphate treatment, was simulated in the laboratory. Commercial products from Parkerizing were used as the treatment agents, and specific process parameters are shown in Table 3.

[0026] [Table 3]

[0027] After processing the sample plates using the method described above, the phosphate crystal coverage and crystal size were microscopically observed using a scanning electron microscope, and the weight of the phosphate film was measured by the chemical dissolution film method. The specific method was as follows.

[0028] (1) Evaluation of phosphate crystal coverage Using a scanning electron microscope (Zeiss SIGMA 500), the phosphate-treated surface of the sample piece was observed at 1000x magnification and evaluated by the ratio of the phosphate film coverage area.

[0029] ◎: Phosphate film coverage = 100% ○: 80% ≤ Phosphate film coverage < 100% △: 60% ≤ Phosphate film coverage < 80% ×: Phosphate film coverage <60% (2) Measurement of phosphate crystal size Using a scanning electron microscope (Zeiss SIGMA 500), the phosphate-treated surface of the sample piece was observed at 2000x magnification. The length dimensions of five random phosphate crystals were measured using a ruler, and the average value was taken.

[0030] (3) Measurement of the weight of the phosphate film First, a 30*70mm phosphate-treated sample plate was weighed (using a Mettler MS-TS analytical balance) and W0 was recorded. Next, the sample piece was immersed in a phosphate film stripping solution (solution: 50g / L anhydrous chromic acid, temperature: 75°C), held for 15 minutes, then removed, washed with deionized water for 40 seconds, dried with cold air, and weighed a second time to record W1. The weight W of the phosphate film was calculated:

[0031]

number

[0032] As can be seen from the results of the implementation (shown in Table 4), Examples 1 to 6 showed good phosphate treatment properties in all evaluation items, and Examples 1, 2, 3, 4, and 6 in particular showed excellent overall performance. As can be seen from the comparison between Examples and Comparative Example 4, the phosphate treatment properties of materials surface-treated with the treatment agent were all significantly improved. As can be seen from the comparison between Example 6 and Comparative Example 1, if the component content of the treatment agent is insufficient, it becomes impossible to effectively improve the phosphate treatment properties of the treated sample plate surface. As can be seen from Examples 1 and 2 and Comparative Example 2, the phosphate treatment properties of the sample plate surface can be optimized by adding an appropriate amount of F-containing compound and metal salt, but if added in excess, the increase in film thickness is detrimental to the rapid growth of the phosphate film, resulting in a decrease in phosphate treatment properties. As can be seen from Example 4 and Comparative Example 3, the excessive addition of surfactants affected the film formation effect of the treatment agent, thereby significantly reducing the optimization effect of the phosphate treatment properties of the treated sample plate surface. As can be seen from Examples 3, 4, and 5, the treatment agent can be applied to typical coating methods such as spraying, impregnation, and roll coating, and has broader process compatibility.

[0033] [Table 4]

[0034] Of course, as those skilled in the art will understand, the above embodiments are merely for illustrative purposes and not to limit the present invention. Any modifications or changes to the above embodiments are included within the scope of the claims of the present invention, as long as they remain within the substantial spirit of the invention.

Claims

1. An aqueous treatment agent prepared by dissolving or dispersing a composition in an aqueous medium, wherein the specific composition of the aqueous treatment agent is: A. Compounds selected from compounds containing fluoride ions; B. Compounds selected from metal ion compounds containing Cu, Zn, Mn, Ni, and Fe; C. Compounds selected from organic acids; D. Compounds selected from surfactants And, The aforementioned compound containing fluoride ions is one or more selected from the group consisting of ammonium fluorotitanate, ammonium fluorozirconate, potassium fluorotitanate, and potassium fluorozirconate. The content of element F in the aqueous treatment agent solution is 0.3 to 1.8 mol / L in molar concentration. The content of metal ion compounds in the aqueous treatment agent solution is 0.05 to 0.6 mol / L in molar concentration. The content of organic acid compounds in the aqueous treatment agent solution is 0.03 to 0.4 mol / L in molar concentration. An environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, characterized in that the amount of the surfactant in the aqueous treatment agent solution is 0.002 to 0.015 mol / L in molar concentration.

2. An environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, characterized in that the content of element F in the aqueous treatment agent solution is 0.3 to 1.7 mol / L.

3. The environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel according to Claim 1, characterized in that the content of element F in the aqueous treatment agent solution is 0.6 to 1.1 mol / L.

4. The Cu-containing metal ion compound is selected from the group consisting of sulfates, carbonates, and nitrates containing copper ions; The Zn-containing metal ion compound is selected from the group consisting of sulfates, phosphates, formates, and acetates containing Zn ions; The metal ion compound containing Mn is selected from the group consisting of phosphates, carbonates, and nitrates containing Mn ions; The Ni-containing metal ion compound is selected from the group consisting of sulfates, nitrates, and carbonates containing Ni ions; The Fe-containing metal ion compound is selected from the group consisting of nitrates and oxalates containing Fe ions. An environmentally friendly water-based treatment agent for improving the phosphate treatment properties of high-strength steel, as described in claim 1.

5. An environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, characterized in that the content of the metal ion compound in the aqueous treatment agent solution is 0.07 to 0.6 mol / L.

6. The environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel according to Claim 1, characterized in that the content of the metal ion compound in the aqueous treatment agent solution is 0.1 to 0.25 mol / L.

7. The aforementioned organic acid compound is an organic acid compound having complex formation or chelate formation function, characterized in that it is an environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel according to claim 1.

8. The environmentally friendly water-based treatment agent for improving the phosphate treatment properties of high-strength steel according to Claim 1, characterized in that the organic acid compound is one or more selected from the group consisting of citric acid, oxalic acid, tannic acid, lactic acid, tartaric acid, and salicylic acid.

9. The environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, characterized in that the content of the organic acid compound in the aqueous treatment agent solution is 0.05 to 0.2 mol / L.

10. The environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, as described in claim 1, characterized in that the compound selected from the surfactants is one or more selected from the group consisting of sodium dodecyl sulfate, sodium dodecyl sulfonate, calcium dodecyl sulfonate, octadecylamine, and triethanolamine.

11. The environmentally friendly aqueous treatment agent for improving the phosphate treatment properties of high-strength steel, characterized in that the amount of the surfactant in the aqueous treatment agent solution is 0.003 to 0.01 mol / L.

12. Furthermore, the environmentally friendly water-based treatment agent for improving the phosphate treatment properties of high-strength steel according to claim 1, characterized in that it contains 0 to 20 parts by weight of water.

13. Use of an environmentally friendly water-based treatment agent to improve the phosphate treatment properties of high-strength steel according to any one of claims 1 to 12 in a continuous production line for pickled high-strength steel or cold-rolled high-strength steel.

14. A method for improving the phosphate treatment properties of high-strength steel, characterized by treating the high-strength steel with an environmentally friendly aqueous treatment agent described in any one of claims 1 to 12 by impregnation, spraying, or roll coating.

15. The method according to claim 14, characterized in that the high-strength steel is high-strength steel that has been pickled or high-strength steel obtained by cold rolling.

16. The method according to claim 14, further comprising treating high-strength steel with a degreasing agent to remove dirt and oil adhering to its surface, then washing it with pure water to remove any remaining alkaline components from the surface, drying it by spraying, and then surface-treating the high-strength steel using the environmentally friendly water-based treatment agent.

17. A high-strength steel characterized by having a nanoscale surface modification layer formed on its surface by drying an environmentally friendly water-based treatment agent according to any one of claims 1 to 12, or a phosphate-treated steel sheet characterized by being a phosphate-treated steel sheet obtained by phosphate-treating the high-strength steel.

18. The phosphate-treated steel sheet according to claim 17, characterized in that the phosphate crystal coverage is ≥ 80%, the phosphate crystal size is ≤ 6 μm, and the weight of the phosphate film is ≥ 2 g / m².

19. The phosphate-treated steel sheet according to claim 18, characterized in that the phosphate crystal coverage rate is 100%.

20. A method for phosphate treatment of high-strength steel, comprising treating the surface of high-strength steel using the method described in claim 14, and then sequentially performing degreasing, washing, surface conditioning, phosphate treatment, washing, and drying on the surface-treated high-strength steel to phosphate treat the high-strength steel.

Images